README
¶
IAVL+ Tree
Note: Requires Go 1.8+
A versioned, snapshottable (immutable) AVL+ tree for persistent data.
The purpose of this data structure is to provide persistent storage for key-value pairs (say to store account balances) such that a deterministic merkle root hash can be computed. The tree is balanced using a variant of the AVL algorithm so all operations are O(log(n)).
Nodes of this tree are immutable and indexed by their hash. Thus any node serves as an immutable snapshot which lets us stage uncommitted transactions from the mempool cheaply, and we can instantly roll back to the last committed state to process transactions of a newly committed block (which may not be the same set of transactions as those from the mempool).
In an AVL tree, the heights of the two child subtrees of any node differ by at most one. Whenever this condition is violated upon an update, the tree is rebalanced by creating O(log(n)) new nodes that point to unmodified nodes of the old tree. In the original AVL algorithm, inner nodes can also hold key-value pairs. The AVL+ algorithm (note the plus) modifies the AVL algorithm to keep all values on leaf nodes, while only using branch-nodes to store keys. This simplifies the algorithm while keeping the merkle hash trail short.
In Ethereum, the analog is Patricia tries. There are tradeoffs. Keys do not need to be hashed prior to insertion in IAVL+ trees, so this provides faster iteration in the key space which may benefit some applications. The logic is simpler to implement, requiring only two types of nodes -- inner nodes and leaf nodes. On the other hand, while IAVL+ trees provide a deterministic merkle root hash, it depends on the order of transactions. In practice this shouldn't be a problem, since you can efficiently encode the tree structure when serializing the tree contents.
Documentation
¶
Overview ¶
Package iavl implements a versioned, snapshottable (immutable) AVL+ tree for persisting key-value pairs.
Basic usage of MutableTree.
import "github.com/tendermint/classic/iavl"
import "github.com/tendermint/classic/db"
...
tree := iavl.NewMutableTree(memdb.NewMemDB(), 128)
tree.IsEmpty() // true
tree.Set([]byte("alice"), []byte("abc"))
tree.SaveVersion(1)
tree.Set([]byte("alice"), []byte("xyz"))
tree.Set([]byte("bob"), []byte("xyz"))
tree.SaveVersion(2)
tree.LatestVersion() // 2
tree.GetVersioned([]byte("alice"), 1) // "abc"
tree.GetVersioned([]byte("alice"), 2) // "xyz"
Proof of existence:
root := tree.Hash()
val, proof, err := tree.GetVersionedWithProof([]byte("bob"), 2) // "xyz", RangeProof, nil
proof.Verify([]byte("bob"), val, root) // nil
Proof of absence:
_, proof, err = tree.GetVersionedWithProof([]byte("tom"), 2) // nil, RangeProof, nil
proof.Verify([]byte("tom"), nil, root) // nil
Now we delete an old version:
tree.DeleteVersion(1)
tree.VersionExists(1) // false
tree.Get([]byte("alice")) // "xyz"
tree.GetVersioned([]byte("alice"), 1) // nil
Can't create a proof of absence for a version we no longer have:
_, proof, err = tree.GetVersionedWithProof([]byte("tom"), 1) // nil, nil, error
Index ¶
- Constants
- Variables
- func Blue(args ...interface{}) string
- func ColoredBytes(data []byte, textColor, bytesColor func(...interface{}) string) string
- func Cyan(args ...interface{}) string
- func Green(args ...interface{}) string
- func IAVLAbsenceOpDecoder(pop merkle.ProofOp) (merkle.ProofOperator, error)
- func IAVLValueOpDecoder(pop merkle.ProofOp) (merkle.ProofOperator, error)
- func PrintTree(tree *ImmutableTree)
- func RegisterWire(cdc *amino.Codec)
- func WriteDOTGraph(w io.Writer, tree *ImmutableTree, paths []PathToLeaf)
- type IAVLAbsenceOp
- type IAVLValueOp
- type ImmutableTree
- func (t *ImmutableTree) Get(key []byte) (index int64, value []byte)
- func (t *ImmutableTree) GetByIndex(index int64) (key []byte, value []byte)
- func (t *ImmutableTree) GetRangeWithProof(startKey []byte, endKey []byte, limit int) (keys, values [][]byte, proof *RangeProof, err error)
- func (t *ImmutableTree) GetWithProof(key []byte) (value []byte, proof *RangeProof, err error)
- func (t *ImmutableTree) Has(key []byte) bool
- func (t *ImmutableTree) Hash() []byte
- func (t *ImmutableTree) Height() int8
- func (t *ImmutableTree) Iterate(fn func(key []byte, value []byte) bool) (stopped bool)
- func (t *ImmutableTree) IterateRange(start, end []byte, ascending bool, fn func(key []byte, value []byte) bool) (stopped bool)
- func (t *ImmutableTree) IterateRangeInclusive(start, end []byte, ascending bool, ...) (stopped bool)
- func (t *ImmutableTree) RenderShape(indent string, encoder NodeEncoder) []string
- func (t *ImmutableTree) Size() int64
- func (t *ImmutableTree) String() string
- func (t *ImmutableTree) Version() int64
- type KeyFormat
- type MutableTree
- func (tree *MutableTree) AvailableVersions() <-chan int64
- func (tree *MutableTree) DeleteVersion(version int64) error
- func (tree *MutableTree) GetImmutable(version int64) (*ImmutableTree, error)
- func (tree *MutableTree) GetVersioned(key []byte, version int64) (index int64, value []byte)
- func (tree *MutableTree) GetVersionedRangeWithProof(startKey, endKey []byte, limit int, version int64) (keys, values [][]byte, proof *RangeProof, err error)
- func (tree *MutableTree) GetVersionedWithProof(key []byte, version int64) ([]byte, *RangeProof, error)
- func (tree *MutableTree) Hash() []byte
- func (tree *MutableTree) IsEmpty() bool
- func (tree *MutableTree) LatestVersion() int64
- func (tree *MutableTree) LazyLoadVersion(targetVersion int64) (int64, error)
- func (tree *MutableTree) Load() (int64, error)
- func (tree *MutableTree) LoadVersion(targetVersion int64) (int64, error)
- func (tree *MutableTree) LoadVersionForOverwriting(targetVersion int64) (int64, error)
- func (tree *MutableTree) Remove(key []byte) ([]byte, bool)
- func (tree *MutableTree) Rollback()
- func (tree *MutableTree) SaveVersion() ([]byte, int64, error)
- func (tree *MutableTree) Set(key, value []byte) bool
- func (tree *MutableTree) String() string
- func (tree *MutableTree) VersionExists(version int64) bool
- func (tree *MutableTree) WorkingHash() []byte
- type Node
- type NodeEncoder
- type PathToLeaf
- type RangeProof
- func (proof *RangeProof) ComputeRootHash() []byte
- func (proof *RangeProof) Keys() (keys [][]byte)
- func (proof *RangeProof) LeftIndex() int64
- func (proof *RangeProof) String() string
- func (proof *RangeProof) StringIndented(indent string) string
- func (proof *RangeProof) Verify(root []byte) error
- func (proof *RangeProof) VerifyAbsence(key []byte) error
- func (proof *RangeProof) VerifyItem(key, value []byte) error
Constants ¶
const ( ANSIReset = "\x1b[0m" ANSIBright = "\x1b[1m" ANSIFgGreen = "\x1b[32m" ANSIFgBlue = "\x1b[34m" ANSIFgCyan = "\x1b[36m" )
const ProofOpIAVLAbsence = "iavl:a"
const ProofOpIAVLValue = "iavl:v"
const Version = "0.12.3"
Version of iavl.
Variables ¶
var ( // ErrInvalidProof is returned by Verify when a proof cannot be validated. ErrInvalidProof = fmt.Errorf("invalid proof") // ErrInvalidInputs is returned when the inputs passed to the function are invalid. ErrInvalidInputs = fmt.Errorf("invalid inputs") // ErrInvalidRoot is returned when the root passed in does not match the proof's. ErrInvalidRoot = fmt.Errorf("invalid root") )
var ErrVersionDoesNotExist = fmt.Errorf("version does not exist")
ErrVersionDoesNotExist is returned if a requested version does not exist.
Functions ¶
func ColoredBytes ¶
ColoredBytes takes in the byte that you would like to show as a string and byte and will display them in a human readable format. If the environment variable TENDERMINT_IAVL_COLORS_ON is set to a non-empty string then different colors will be used for bytes and strings.
func IAVLAbsenceOpDecoder ¶
func IAVLAbsenceOpDecoder(pop merkle.ProofOp) (merkle.ProofOperator, error)
func IAVLValueOpDecoder ¶
func IAVLValueOpDecoder(pop merkle.ProofOp) (merkle.ProofOperator, error)
func PrintTree ¶
func PrintTree(tree *ImmutableTree)
PrintTree prints the whole tree in an indented form.
func RegisterWire ¶
func WriteDOTGraph ¶
func WriteDOTGraph(w io.Writer, tree *ImmutableTree, paths []PathToLeaf)
Types ¶
type IAVLAbsenceOp ¶
type IAVLAbsenceOp struct {
// To encode in ProofOp.Data.
// Proof is nil for an empty tree.
// The hash of an empty tree is nil.
Proof *RangeProof `json:"proof"`
// contains filtered or unexported fields
}
IAVLAbsenceOp takes a key as its only argument
If the produced root hash matches the expected hash, the proof is good.
func NewIAVLAbsenceOp ¶
func NewIAVLAbsenceOp(key []byte, proof *RangeProof) IAVLAbsenceOp
func (IAVLAbsenceOp) GetKey ¶
func (op IAVLAbsenceOp) GetKey() []byte
func (IAVLAbsenceOp) ProofOp ¶
func (op IAVLAbsenceOp) ProofOp() merkle.ProofOp
func (IAVLAbsenceOp) String ¶
func (op IAVLAbsenceOp) String() string
type IAVLValueOp ¶
type IAVLValueOp struct {
// To encode in ProofOp.Data.
// Proof is nil for an empty tree.
// The hash of an empty tree is nil.
Proof *RangeProof `json:"proof"`
// contains filtered or unexported fields
}
IAVLValueOp takes a key and a single value as argument and produces the root hash.
If the produced root hash matches the expected hash, the proof is good.
func NewIAVLValueOp ¶
func NewIAVLValueOp(key []byte, proof *RangeProof) IAVLValueOp
func (IAVLValueOp) GetKey ¶
func (op IAVLValueOp) GetKey() []byte
func (IAVLValueOp) ProofOp ¶
func (op IAVLValueOp) ProofOp() merkle.ProofOp
func (IAVLValueOp) String ¶
func (op IAVLValueOp) String() string
type ImmutableTree ¶
type ImmutableTree struct {
// contains filtered or unexported fields
}
ImmutableTree is a container for an immutable AVL+ ImmutableTree. Changes are performed by swapping the internal root with a new one, while the container is mutable. Note that this tree is not thread-safe.
func NewImmutableTree ¶
func NewImmutableTree(db dbm.DB, cacheSize int) *ImmutableTree
NewImmutableTree creates both in-memory and persistent instances
func (*ImmutableTree) Get ¶
func (t *ImmutableTree) Get(key []byte) (index int64, value []byte)
Get returns the index and value of the specified key if it exists, or nil and the next index, if it doesn't.
func (*ImmutableTree) GetByIndex ¶
func (t *ImmutableTree) GetByIndex(index int64) (key []byte, value []byte)
GetByIndex gets the key and value at the specified index.
func (*ImmutableTree) GetRangeWithProof ¶
func (t *ImmutableTree) GetRangeWithProof(startKey []byte, endKey []byte, limit int) (keys, values [][]byte, proof *RangeProof, err error)
GetRangeWithProof gets key/value pairs within the specified range and limit.
func (*ImmutableTree) GetWithProof ¶
func (t *ImmutableTree) GetWithProof(key []byte) (value []byte, proof *RangeProof, err error)
GetWithProof gets the value under the key if it exists, or returns nil. A proof of existence or absence is returned alongside the value.
func (*ImmutableTree) Has ¶
func (t *ImmutableTree) Has(key []byte) bool
Has returns whether or not a key exists.
func (*ImmutableTree) Height ¶
func (t *ImmutableTree) Height() int8
Height returns the height of the tree.
func (*ImmutableTree) Iterate ¶
func (t *ImmutableTree) Iterate(fn func(key []byte, value []byte) bool) (stopped bool)
Iterate iterates over all keys of the tree, in order.
func (*ImmutableTree) IterateRange ¶
func (t *ImmutableTree) IterateRange(start, end []byte, ascending bool, fn func(key []byte, value []byte) bool) (stopped bool)
IterateRange makes a callback for all nodes with key between start and end non-inclusive. If either are nil, then it is open on that side (nil, nil is the same as Iterate)
func (*ImmutableTree) IterateRangeInclusive ¶
func (t *ImmutableTree) IterateRangeInclusive(start, end []byte, ascending bool, fn func(key, value []byte, version int64) bool) (stopped bool)
IterateRangeInclusive makes a callback for all nodes with key between start and end inclusive. If either are nil, then it is open on that side (nil, nil is the same as Iterate)
func (*ImmutableTree) RenderShape ¶
func (t *ImmutableTree) RenderShape(indent string, encoder NodeEncoder) []string
RenderShape provides a nested tree shape, ident is prepended in each level Returns an array of strings, one per line, to join with "\n" or display otherwise
func (*ImmutableTree) Size ¶
func (t *ImmutableTree) Size() int64
Size returns the number of leaf nodes in the tree.
func (*ImmutableTree) String ¶
func (t *ImmutableTree) String() string
String returns a string representation of Tree.
func (*ImmutableTree) Version ¶
func (t *ImmutableTree) Version() int64
Version returns the version of the tree.
type KeyFormat ¶
type KeyFormat struct {
// contains filtered or unexported fields
}
Provides a fixed-width lexicographically sortable []byte key format
func NewKeyFormat ¶
Create a []byte key format based on a single byte prefix and fixed width key segments each of whose length is specified by by the corresponding element of layout.
For example, to store keys that could index some objects by a version number and their SHA256 hash using the form: 'c<version uint64><hash [32]byte>' then you would define the KeyFormat with:
var keyFormat = NewKeyFormat('c', 8, 32)
Then you can create a key with:
func ObjectKey(version uint64, objectBytes []byte) []byte {
hasher := sha256.New()
hasher.Sum(nil)
return keyFormat.Key(version, hasher.Sum(nil))
}
func (*KeyFormat) Key ¶
Format the args passed into the key format - will panic if the arguments passed do not match the length of the segment to which they correspond. When called with no arguments returns the raw prefix (useful as a start element of the entire keys space when sorted lexicographically).
func (*KeyFormat) KeyBytes ¶
Format the byte segments into the key format - will panic if the segment lengths do not match the layout.
type MutableTree ¶
type MutableTree struct {
*ImmutableTree // The current, working tree.
// contains filtered or unexported fields
}
MutableTree is a persistent tree which keeps track of versions.
func NewMutableTree ¶
func NewMutableTree(db dbm.DB, cacheSize int) *MutableTree
NewMutableTree returns a new tree with the specified cache size and datastore.
func (*MutableTree) AvailableVersions ¶
func (tree *MutableTree) AvailableVersions() <-chan int64
AvailableVersions returns all available versions in ascending order
func (*MutableTree) DeleteVersion ¶
func (tree *MutableTree) DeleteVersion(version int64) error
DeleteVersion deletes a tree version from disk. The version can then no longer be accessed.
func (*MutableTree) GetImmutable ¶
func (tree *MutableTree) GetImmutable(version int64) (*ImmutableTree, error)
GetImmutable loads an ImmutableTree at a given version for querying
func (*MutableTree) GetVersioned ¶
func (tree *MutableTree) GetVersioned(key []byte, version int64) ( index int64, value []byte, )
GetVersioned gets the value at the specified key and version.
func (*MutableTree) GetVersionedRangeWithProof ¶
func (tree *MutableTree) GetVersionedRangeWithProof(startKey, endKey []byte, limit int, version int64) ( keys, values [][]byte, proof *RangeProof, err error, )
GetVersionedRangeWithProof gets key/value pairs within the specified range and limit.
func (*MutableTree) GetVersionedWithProof ¶
func (tree *MutableTree) GetVersionedWithProof(key []byte, version int64) ([]byte, *RangeProof, error)
GetVersionedWithProof gets the value under the key at the specified version if it exists, or returns nil.
func (*MutableTree) Hash ¶
func (tree *MutableTree) Hash() []byte
Hash returns the hash of the latest saved version of the tree, as returned by SaveVersion. If no versions have been saved, Hash returns nil.
func (*MutableTree) IsEmpty ¶
func (tree *MutableTree) IsEmpty() bool
IsEmpty returns whether or not the tree has any keys. Only trees that are not empty can be saved.
func (*MutableTree) LatestVersion ¶
func (tree *MutableTree) LatestVersion() int64
LatestVersion returns the latest version.
func (*MutableTree) LazyLoadVersion ¶
func (tree *MutableTree) LazyLoadVersion(targetVersion int64) (int64, error)
LazyLoadVersion attempts to lazy load only the specified target version without loading previous roots/versions. Lazy loading should be used in cases where only reads are expected. Any writes to a lazy loaded tree may result in unexpected behavior. If the targetVersion is non-positive, the latest version will be loaded by default. If the latest version is non-positive, this method performs a no-op. Otherwise, if the root does not exist, an error will be returned.
func (*MutableTree) Load ¶
func (tree *MutableTree) Load() (int64, error)
Load the latest versioned tree from disk.
func (*MutableTree) LoadVersion ¶
func (tree *MutableTree) LoadVersion(targetVersion int64) (int64, error)
Returns the version number of the latest version found
func (*MutableTree) LoadVersionForOverwriting ¶
func (tree *MutableTree) LoadVersionForOverwriting(targetVersion int64) (int64, error)
LoadVersionOverwrite returns the version number of targetVersion. Higher versions' data will be deleted.
func (*MutableTree) Remove ¶
func (tree *MutableTree) Remove(key []byte) ([]byte, bool)
Remove removes a key from the working tree.
func (*MutableTree) Rollback ¶
func (tree *MutableTree) Rollback()
Rollback resets the working tree to the latest saved version, discarding any unsaved modifications.
func (*MutableTree) SaveVersion ¶
func (tree *MutableTree) SaveVersion() ([]byte, int64, error)
SaveVersion saves a new tree version to disk, based on the current state of the tree. Returns the hash and new version number.
func (*MutableTree) Set ¶
func (tree *MutableTree) Set(key, value []byte) bool
Set sets a key in the working tree. Nil values are not supported.
func (*MutableTree) String ¶
func (tree *MutableTree) String() string
String returns a string representation of the tree.
func (*MutableTree) VersionExists ¶
func (tree *MutableTree) VersionExists(version int64) bool
VersionExists returns whether or not a version exists.
func (*MutableTree) WorkingHash ¶
func (tree *MutableTree) WorkingHash() []byte
WorkingHash returns the hash of the current working tree.
type Node ¶
type Node struct {
// contains filtered or unexported fields
}
Node represents a node in a Tree.
func MakeNode ¶
MakeNode constructs an *Node from an encoded byte slice.
The new node doesn't have its hash saved or set. The caller must set it afterwards.
func (*Node) PathToLeaf ¶
func (node *Node) PathToLeaf(t *ImmutableTree, key []byte) (PathToLeaf, *Node, error)
If the key does not exist, returns the path to the next leaf left of key (w/ path), except when key is less than the least item, in which case it returns a path to the least item.
type NodeEncoder ¶
NodeEncoder will take an id (hash, or key for leaf nodes), the depth of the node, and whether or not this is a leaf node. It returns the string we wish to print, for iaviwer
type PathToLeaf ¶
type PathToLeaf []proofInnerNode
PathToLeaf represents an inner path to a leaf node. Note that the nodes are ordered such that the last one is closest to the root of the tree.
func (PathToLeaf) String ¶
func (pl PathToLeaf) String() string
type RangeProof ¶
type RangeProof struct {
// You don't need the right path because
// it can be derived from what we have.
LeftPath PathToLeaf `json:"left_path"`
InnerNodes []PathToLeaf `json:"inner_nodes"`
Leaves []proofLeafNode `json:"leaves"`
// contains filtered or unexported fields
}
func (*RangeProof) ComputeRootHash ¶
func (proof *RangeProof) ComputeRootHash() []byte
ComputeRootHash computes the root hash with leaves. Returns nil if error or proof is nil. Does not verify the root hash.
func (*RangeProof) Keys ¶
func (proof *RangeProof) Keys() (keys [][]byte)
Keys returns all the keys in the RangeProof. NOTE: The keys here may include more keys than provided by tree.GetRangeWithProof or MutableTree.GetVersionedRangeWithProof. The keys returned there are only in the provided [startKey,endKey){limit} range. The keys returned here may include extra keys, such as: - the key before startKey if startKey is provided and doesn't exist; - the key after a queried key with tree.GetWithProof, when the key is absent.
func (*RangeProof) LeftIndex ¶
func (proof *RangeProof) LeftIndex() int64
The index of the first leaf (of the whole tree). Returns -1 if the proof is nil.
func (*RangeProof) String ¶
func (proof *RangeProof) String() string
String returns a string representation of the proof.
func (*RangeProof) StringIndented ¶
func (proof *RangeProof) StringIndented(indent string) string
func (*RangeProof) Verify ¶
func (proof *RangeProof) Verify(root []byte) error
Verify that proof is valid.
func (*RangeProof) VerifyAbsence ¶
func (proof *RangeProof) VerifyAbsence(key []byte) error
Verify that proof is valid absence proof for key. Does not assume that the proof itself is valid. For that, use Verify(root).
func (*RangeProof) VerifyItem ¶
func (proof *RangeProof) VerifyItem(key, value []byte) error
Also see LeftIndex(). Verify that a key has some value. Does not assume that the proof itself is valid, call Verify() first.
Source Files
Directories